The patch titled
Subject: mm: huge_memory: debugfs for file-backed THP split
has been added to the -mm tree. Its filename is
mm-huge_memory-debugfs-for-file-backed-thp-split.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-huge_memory-debugfs-for-file-backed-thp-split.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-huge_memory-debugfs-for-file-backed-thp-split.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm: huge_memory: debugfs for file-backed THP split
Further extend <debugfs>/split_huge_pages to accept
"<path>,<pgoff_start>,<pgoff_end>" for file-backed THP split tests since
tmpfs may have file backed by THP that mapped nowhere.
Update selftest program to test file-backed THP split too.
Link: https://lkml.kernel.org/r/20210331235309.332292-2-zi.yan@xxxxxxxx
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Sandipan Das <sandipan@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mika Penttila <mika.penttila@xxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 90 +++++++++++-
tools/testing/selftests/vm/split_huge_page_test.c | 82 ++++++++++
2 files changed, 166 insertions(+), 6 deletions(-)
--- a/mm/huge_memory.c~mm-huge_memory-debugfs-for-file-backed-thp-split
+++ a/mm/huge_memory.c
@@ -3050,6 +3050,65 @@ out:
return ret;
}
+static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
+ pgoff_t off_end)
+{
+ struct filename *file;
+ struct file *candidate;
+ struct address_space *mapping;
+ int ret = -EINVAL;
+ pgoff_t index;
+ int nr_pages = 1;
+ unsigned long total = 0, split = 0;
+
+ file = getname_kernel(file_path);
+ if (IS_ERR(file))
+ return ret;
+
+ candidate = file_open_name(file, O_RDONLY, 0);
+ if (IS_ERR(candidate))
+ goto out;
+
+ pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
+ file_path, off_start, off_end);
+
+ mapping = candidate->f_mapping;
+
+ for (index = off_start; index < off_end; index += nr_pages) {
+ struct page *fpage = pagecache_get_page(mapping, index,
+ FGP_ENTRY | FGP_HEAD, 0);
+
+ nr_pages = 1;
+ if (xa_is_value(fpage) || !fpage)
+ continue;
+
+ if (!is_transparent_hugepage(fpage))
+ goto next;
+
+ total++;
+ nr_pages = thp_nr_pages(fpage);
+
+ if (!trylock_page(fpage))
+ goto next;
+
+ if (!split_huge_page(fpage))
+ split++;
+
+ unlock_page(fpage);
+next:
+ put_page(fpage);
+ cond_resched();
+ }
+
+ filp_close(candidate, NULL);
+ ret = 0;
+
+ pr_debug("%lu of %lu file-backed THP split\n", split, total);
+out:
+ putname(file);
+ return ret;
+}
+
#define MAX_INPUT_BUF_SZ 255
static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
@@ -3057,7 +3116,8 @@ static ssize_t split_huge_pages_write(st
{
static DEFINE_MUTEX(split_debug_mutex);
ssize_t ret;
- char input_buf[MAX_INPUT_BUF_SZ]; /* hold pid, start_vaddr, end_vaddr */
+ /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
+ char input_buf[MAX_INPUT_BUF_SZ];
int pid;
unsigned long vaddr_start, vaddr_end;
@@ -3072,6 +3132,34 @@ static ssize_t split_huge_pages_write(st
goto out;
input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
+
+ if (input_buf[0] == '/') {
+ char *tok;
+ char *buf = input_buf;
+ char file_path[MAX_INPUT_BUF_SZ];
+ pgoff_t off_start = 0, off_end = 0;
+ size_t input_len = strlen(input_buf);
+
+ tok = strsep(&buf, ",");
+ if (tok) {
+ strncpy(file_path, tok, MAX_INPUT_BUF_SZ);
+ } else {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
+ if (ret != 2) {
+ ret = -EINVAL;
+ goto out;
+ }
+ ret = split_huge_pages_in_file(file_path, off_start, off_end);
+ if (!ret)
+ ret = input_len;
+
+ goto out;
+ }
+
ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
if (ret == 1 && pid == 1) {
split_huge_pages_all();
--- a/tools/testing/selftests/vm/split_huge_page_test.c~mm-huge_memory-debugfs-for-file-backed-thp-split
+++ a/tools/testing/selftests/vm/split_huge_page_test.c
@@ -7,11 +7,13 @@
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
+#include <stdarg.h>
#include <unistd.h>
#include <inttypes.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
+#include <sys/mount.h>
#include <malloc.h>
#include <stdbool.h>
@@ -24,6 +26,9 @@ uint64_t pmd_pagesize;
#define SMAP_PATH "/proc/self/smaps"
#define INPUT_MAX 80
+#define PID_FMT "%d,0x%lx,0x%lx"
+#define PATH_FMT "%s,0x%lx,0x%lx"
+
#define PFN_MASK ((1UL<<55)-1)
#define KPF_THP (1UL<<22)
@@ -87,13 +92,16 @@ static int write_file(const char *path,
return (unsigned int) numwritten;
}
-static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end)
+static void write_debugfs(const char *fmt, ...)
{
char input[INPUT_MAX];
int ret;
+ va_list argp;
+
+ va_start(argp, fmt);
+ ret = vsnprintf(input, INPUT_MAX, fmt, argp);
+ va_end(argp);
- ret = snprintf(input, INPUT_MAX, "%d,0x%lx,0x%lx", pid, vaddr_start,
- vaddr_end);
if (ret >= INPUT_MAX) {
printf("%s: Debugfs input is too long\n", __func__);
exit(EXIT_FAILURE);
@@ -183,7 +191,8 @@ void split_pmd_thp(void)
}
/* split all THPs */
- write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len);
+ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
+ (uint64_t)one_page + len);
for (i = 0; i < len; i++)
if (one_page[i] != (char)i) {
@@ -274,7 +283,7 @@ void split_pte_mapped_thp(void)
}
/* split all remapped THPs */
- write_debugfs(getpid(), (uint64_t)pte_mapped,
+ write_debugfs(PID_FMT, getpid(), (uint64_t)pte_mapped,
(uint64_t)pte_mapped + pagesize * 4);
/* smap does not show THPs after mremap, use kpageflags instead */
@@ -300,6 +309,68 @@ void split_pte_mapped_thp(void)
close(kpageflags_fd);
}
+void split_file_backed_thp(void)
+{
+ int status;
+ int fd;
+ ssize_t num_written;
+ char tmpfs_template[] = "/tmp/thp_split_XXXXXX";
+ const char *tmpfs_loc = mkdtemp(tmpfs_template);
+ char testfile[INPUT_MAX];
+ uint64_t pgoff_start = 0, pgoff_end = 1024;
+
+ printf("Please enable pr_debug in split_huge_pages_in_file() if you need more info.\n");
+
+ status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
+
+ if (status) {
+ printf("Unable to create a tmpfs for testing\n");
+ exit(EXIT_FAILURE);
+ }
+
+ status = snprintf(testfile, INPUT_MAX, "%s/thp_file", tmpfs_loc);
+ if (status >= INPUT_MAX) {
+ printf("Fail to create file-backed THP split testing file\n");
+ goto cleanup;
+ }
+
+ fd = open(testfile, O_CREAT|O_WRONLY);
+ if (fd == -1) {
+ perror("Cannot open testing file\n");
+ goto cleanup;
+ }
+
+ /* write something to the file, so a file-backed THP can be allocated */
+ num_written = write(fd, tmpfs_loc, sizeof(tmpfs_loc));
+ close(fd);
+
+ if (num_written < 1) {
+ printf("Fail to write data to testing file\n");
+ goto cleanup;
+ }
+
+ /* split the file-backed THP */
+ write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end);
+
+ status = unlink(testfile);
+ if (status)
+ perror("Cannot remove testing file\n");
+
+cleanup:
+ status = umount(tmpfs_loc);
+ if (status) {
+ printf("Unable to umount %s\n", tmpfs_loc);
+ exit(EXIT_FAILURE);
+ }
+ status = rmdir(tmpfs_loc);
+ if (status) {
+ perror("cannot remove tmp dir");
+ exit(EXIT_FAILURE);
+ }
+
+ printf("file-backed THP split test done, please check dmesg for more information\n");
+}
+
int main(int argc, char **argv)
{
if (geteuid() != 0) {
@@ -313,6 +384,7 @@ int main(int argc, char **argv)
split_pmd_thp();
split_pte_mapped_thp();
+ split_file_backed_thp();
return 0;
}
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-huge_memory-a-new-debugfs-interface-for-splitting-thp-tests.patch
mm-huge_memory-debugfs-for-file-backed-thp-split.patch
